We use Rasa NLU for intent classification & entity extraction,
but you are free to use other NLU services like wit.ai, api.ai, or LUIS.ai. If you
want to use Rasa NLU make sure to follow the installation instructions of the
NLU docs as well.
In fact, you don’t need to use NLU at all, if your messaging app uses buttons
rather than free text.